The indicators should be applied to a curated, representative set of species - 100 to several thousand species per country, depending on a country’s biodiversity, data capacity, and resources for CBD reporting. Approximately 100 species is likely a minimum to represent diverse habitats, taxonomic groups, commonness/ rarity, and threat status. However, if 100 cannot be collected, any amount of data is important.
The two genetic diversity indicators are:
The first indicator is based on comparing the effective population size of each population Ne to a critical threshold (e.g. Ne = 500). For many species, it is sufficient and appropriate to use the census size Nc (the number of living adults) as a proxy for Ne, and a threshold of Nc = 5000 mature individuals. Below this threshold, a population rapidly loses genetic diversity, can become inbred, and starts to lose ability to adapt to environmental change.
The second indicator is based on comparing the current number of populations that exist to a prior/ historic assessment of the number of populations . This reflects loss of populations to human-induced changes, with 50-200 years ago as a baseline (depending on the country). If counts of populations existing and lost are not available, a proportion (or percentage) of the species’ range are lost is an acceptable substitute. Lastly, if this is not available, some estimate of overall decline is acceptable (details will be explained below).
The primary undertaking is to gather the data on populations for each species. This is a challenge because there is no global, standard database of population census size (The Living Planet Index for example does not measure full population census, and not all Red List species have census size for each population). But the census size of many populations of many species is available in different reports and databases, in more or less easy ways to extract. This guidance document will explain how to gather and use the necessary data, from diverse sources, in a standard way.
As noted above, a third indicator exists, which is to count the number of genetic studies available for that species, if any. Although this does not directly relate to maintenance of genetic diversity or preventing genetic erosion, performing genetic studies and collecting genetic data correlates to management actions designed to manage genetic diversity- such studies help understand needed management actions and to guide them. So we will also collect information on whether genetic studies exist for species, for reporting on indicator 3. However, this project will not use genetic datasets to calculate the Ne or Ncbecause reanalysis of data is time prohibitive- we are not downloading and analyzing genetic data.
The Project Purpose This project was planned in 2021 and initiated in 2022 to test the indicators in a small number of countries. The project goal is for each country team to evaluate >100 species (per country) to determine (a) how many species have the required data, (b) to extract the data when possible for indicator calculation, and (c) to identify barriers encountered so that this guidance document and indicator calculation can be improved for larger scale use by more countries to inform the CBD framework. The project will also highlight species and regions where data is deficient, or where there is high uncertainty in the estimates.